This research project is directed toward a study of the effect of mammary adenocarcinoma on steroid metabolizing enzymes in order to determine whether the presence of mammary tumors results in altered steroid metabolism by livers of tumor bearing rats. Steroid delta-4-5-alpha-reductase, delta-4-5-beta reductase, 17-beta-hydroxysteroid dehydrogenase, 3-hydroxysteroid dehydrogenase and 16-alpha-hydroxylase activity will be determined by in vitro studies involving either a spectrophotometric assay or incubations of labelled steroid substrates followed by isolation, separation on thin-layer chromatography and crystallization of radio-labelled metabolites to constant specific activity before and after derivative formation. These studies will be correlated with data obtained from in vivo studies involving the administration of the appropriate labelled substrate followed by urine analysis for the appropriate metabolite using separation and purification to constant specific activity. The effect of surgical removal of tumor and cell-free tumor extract administration will be studied in order to determine whether the tumor contains a factor(s) responsible for altered steroid metabolism.